Two-stage tobacco smoke filter

Claim 1

Apparatus for filtering tobacco smoke, comprising: a generally tubular element connectable at an upstream end to a tobacco-containing body and defining a generally cylindrical chamber through which tobacco smoke is drawn toward a downstream end of said element; funnel means adjacent the upstream end of said tubular element, said funnel means terminating downstream in an apex forming an axial capillary orifice for accelerating smoke in a high velocity stream toward the downstream end of said tubular element, said funnel means forming in cooperation with the interior wall of said tubular element an expansion chamber into which said stream is discharged whereby said smoke is decelerated in said expansion chamber; a parabolic disc for collecting particulate material, said parabolic disc being positioned downstream of said orifice, the axis of said parabolic disc being in the path of smoke discharged from said orifice, said parabolic disc having a periphery closely spaced from the interior walls of said tubular element, whereby said smoke is again accelerated to flow at high velocity around said periphery, thereby inducing turbulence adjacent the downstream side of said parabolic disc and causing the deposition of particulate material thereon; means downstream of said parabolic disc for defining an additional expansion chamber and a flow path to the exterior of said tubular element, said means comprising a transverse circular end disc positioned in the downstream end of said tubular element and having a central opening therein, and a tube extending from said central opening to the downstream face of said parabolic disc, said additional chamber being defined by the said circular disc, said parabolic disc, said tubular element and said tube, said tube having side openings defining a flow path from the said additional expansion chamber to the interior of said tube.